Method for felting wafers in waferboard production

ABSTRACT

1.The method of felting wood wafers in waferboard production, which comprises directing the wafers on to a spinning cone within a confined space and be thrown radially off said cone into the open upper ends of a plurality of tubes arranged around the cone, the lower ends of said tubes arranged around the cone, the lower ends of said tubes being arranged in spaced rows extending transversely of and spaced above a path along which supporting plates are moved, said tubes distributing the wafers evenly on to the moving plates across the width thereof to form thereon felted mats of predetermined thickness and density.

Nov. 26, 1974 w, WATKINS 3,851,031

METHOD FOR FELTING WAFERS 1N WAFERBOARD PRODUCTION III-"I... III-I"...

NOV. 26, 1974 w w s 33,851,031

METHOD FOR FELTING WAFERS IN WAFFIRHQAHD 'IRODUC'IIiON Filed Dec. 27, 1972 2 Sheets-Sheet 13 United States Patent US. Cl. 264-109 6 Claims ABSTRACT OF THE DISCLOSURE A method in which wood wafers are directed onto a spinning cone to be thrown off radially into a plurality of tubes having open ends arranged around the cone. The opposite ends of these tubes are arranged in a plurality of rows which extend transversely of a path along which supporting plates are moved so that the wafers are deposited on the plates to form mats and are evenly distributed across the plates.

This invention relates to methods for felting wood wafers in the production of waferboard.

Although this invention is primarily concerned with the felting of what is known in the trade as wafers, it can equally be used for felting wood flakes, wood particles, wood chips and the like, and the term wafer is intended to include all of these.

In the production of waferboard, wood wafers are deposited upon caul plates or the like to form a mat of substantially uniform thickness and density. The caul plates are moved into a hot press where the wafer mats are compressed under heat and pressure to produce waferboards of predetermined thicknesses.

The thickness of the wafers used in the manufacture of Waferboard, is in the order of .010 to 0.060 inch. This means that errors in placement of only a few wafers can cause a large change in the thickness of the panels. The pressing operation can compensate to some extent for variations in the number of wafers or in the variations in the mat size. However, this will result in variations in the density of the panel produced, and this density change can seriously aifect the strength properties of these panels.

It is well known in the industry to use levelling rolls for maintaining a constant volume of wafers or particles in the mats. However, these levelling rolls are only sensitive to metering by volume, while the bulk density of the mat of particles can vary considerably, resulting in variations of density and of thickness of the panel produced. In waferboard production, a panel thickness tolerance of plus or minus .030 inch is the maximum which can be tolerated for such uses as roof sheathing, sub-floors or underlayment.

The present invention overcomes these problems by applying the waters at a multitude of points on to the forming line while still maintaining the uniform structure of the mat.

The method according to this invention of felting wood wafers comprises directing the wafers on to a spinning cone to be thrown radially off said cone into the open upper ends of aplurality of tubes arranged around the cone, the lower ends of said tubes being arranged in spaced rows extending transversely of and spaced above a path along which supporting or caul plates are moved, said tubes distributing the wafers evenly on to the moving plates across the width thereof to form thereon felted mats of predetermined thickness and density.

The wafers are generally fed at a uniform rate to the cone but by the very nature of the production of these wafers and the wafers themselves there is bound to be variations in the feed rate or the density of the wafers being fed to the apparatus at any given time. The spinning cone spreads out or directs the wafers to the upper ends of the tubes so that changes in the rate of feed do not materially affect distribution of the wafers. The wafers are mainly directed against the apex of the cone but if the discharge is a little off the center, the arrangement of the upper and lower ends of the tubes is such that there still is an even distribution of the wafers across the mats being formed.

Apparatus for felting wafers in the production of waferboard in accordance with this invention comprises a container having a peripheral wall, a cone mounted for rotation in the container centrally thereof, power means for spinning the cone, means for directing a stream of wood wafers on to the cone, conveying means for moving supporting plates along a path spaced below said container, and a plurality of tubes having upper ends opening into the container and arranged around the cone, said tubes having lower ends arranged in rows extending transversely of said path and across the width of the supporting plates, said tubes distributing the wafers evenly on to the moving plates across the width thereof to form thereon felted mats of predetermined thickness and density.

The method and apparatus will be more clearly understood by reference to the accompanying drawings, in which FIG. 1 is a cross-section through the supporting plate path and showing the apparatus in elevation,

FIG. 2 is a plan view of the apparatus,

FIG. 3 is a side elevation of this apparatus, and

FIGS. 4 and 5 are diagrams which help to illustrate the method involved in this apparatus.

Referring to the drawings, 10 is felting or distributing apparatus in accordance with this invention which is located above a conveyor belt 11 for moving supporting plates, such as caul plates 12, along a path indicated by arrow 13 beneath apparatus 10.

Apparatus 10 includes a contain-er 20 suitably suported above conveyor 11 and having a bottom 22 and an annular peripheral wall 23. A cone 26 is supported in any suitable manner in the container with its base just above the bottom 22. In this example, the cone is mounted on a vertical shaft 28 which extends through bottom 22 and is rotated in any suitable manner, such as by means of an electric motor 29, which is operatively connected to the drive shaft by means of a belt and pulley arrangement 30, see FIG. 3. The peripheral edge 32 of cone 26 is spaced from container wall 23, and a plurality of tubes 35 have upper ends communicating with the interior of container 20 through openings 36 formed in bottom 22 and arranged around the cone. It will be noted that the surface 38 of the cone extends downwardly in a curve from the cone apex 39 to the peripheral edge 32 of the cone. Wafers are directed in to the apex of the cone by tube 40.

Tubes 35 extend downwardly from container 20 and have lower ends 42 that are arranged in four rows E, F, G and H above and extending transversely of the path of travel 13 of the caul plates 12. By referring to FIG. 5, it will be seen that each of these rows extends completely across the caul plate so that flakes, wafers or particulate material travelling downwardly from tubes 35 are distributed across the width of the plate.

It is essential to distribute the wafers evenly across each caul plate and to form a mat thereon of uniform thickness and density. This is greatly assisted by the arrangement of the lower ends of the tubes in the rows E to H. In the diagram of FIG. 4, tubes are numbered 1 to 6, and there is a group of these tubes 1 to 6 each quadrant of the circle formed by container 20. The tubes in the different quadrants are also labelled a, b, c and d. The upper ends of the tubes are numbered 1 to 6 in sequence in each quadrant, and the letter of the row in which the lower end of each tube is positioned appears opposite each number. For example, tubes In to M have their lower ends opening respectively into rows E, F, E, G, H, G. by referring to FIG. 5 it will be seen that row E, for example, includes tubes 1a, 2d 3a, 40, 5b, 6c. The reason for this is that should the feed of the wafers get off centre, that is, off apex 39, or if there is a sudden mass of the flakes directed to container 20, there still will be an even distribution of the flakes across the mat being formed. Taking the tubes of quadrant a, for example, it will be seen that 1a is in row E, 2a in row F, 3a in row E, 4a 'in row G, 5a in row H, and 6a in row G, and these in effect make a line across the mat.

Although the spinning cone 26 tends to distribute the wafers evenly around the upper ends of the tubes even when the feed tube 40 is off centre or there is a sudden mass of flakes directed into the container, this particular arrangement of the lower ends of the tubes helps in the equal distribution of the flakes across the mat. The distribution is always evenly across the mat, although there can be slight differences in the longitudinal direction owing to the fact that the lower ends of the tubes are in ditferent rows and these are spaced longitudinally of the mat. However, the longitudinal spacing is relatively small, and in actual practice mats of uniform thickness and substantially uniform density are formed.

It will be understood that the actual arrangement of the lower ends of the tubes may be difierent from that illustrated in FIG. 5, but the main thing is that the tubes of each quadrant form a line across the path of travel of the mat, although this line is not necessarily straight across. The advantage of this will be seen from the following. If, for example, there is a larger than usual amount of flakes directed to the adjacent ends of quadrants a and d, affecting tubes 1 to 3 and 4 of quadrant a and tubes 5 and 6 of quadrant d, the line would be as follows across the mat: laE, ZaF, 3aE, 4aG, SdG, and SdH. Thus, no matter where there is a concentration of flakes around the upper ends of the tubes, the discharge at the increased rate will in eflect be completely across the path of travel.

The lower ends of the tubes are flexible and not necessarily directly in line behind one another. In some cases it is desirable to move the ends slightly out of position to compensate for small irregularities in the mat. Those can be caused by excessive bending of the tubes thus interfering with the free fall of the wafers after they enter the tube.

In the production of waferboards there usually are a plurality of these felting heads, each head being a container with its tubes, arranged in succession over the path of the supporting plates. For example, there can be four of these heads, in which case the first and fourth heads, with respect to the direction of movement of the plates, direct wafers prepared for the face layers or sections of the waferboards on to the plates, and the second and third heads direct wafers for the inner or core section of the boards. Usually, better quality wafers are used for the face layers.

I claim:

1. The method of felting wood wafers in waferboard production, which comprises directing the wafers on to a spinning cone within a confined space and to be thrown radially off said cone into the open upper ends of a plurality of tubes arranged around the cone, the lower ends of said tubes being arranged in spaced rows extending transversely of and spaced above a path along which supporting plates are moved, said tubes distributing the wafers evenly on to the moving plates across the width thereof to form thereon felted mats of predetermined thickness and density.

2. The method as claimed in claim 1 in which the wafers are directed in a stream on to the apex of the cone.

3. The method as claimed in claim 1 in which the upper ends of said tubes are arranged substantially in a circle, and the lower ends of the tubes of each quadrant of the circle are arranged in various rows of the tubes.

4. The method as claimed in claim 1 in which the upper ends of said tubes are arranged substantially in a circle with six tubes in each quadrant of the circle, and the lower ends of the tubes are arranged in four transverse rows with the ends of the tubes of each quadrant in various rows.

5. The method as claimed in claim 2 in which the upper ends of said tubes are arranged substantially in a circle, and the lower ends of the tubes of each quadrant of the circle are arranged in various rows of the tubes.

6. The method as claimed in claim 2 in which the upper ends of said tubes are arranged substantially in a circle with six tubes in each quadrant of the circle, and the lower ends of the tubes are arranged in four transverse rows with the ends of the tubes of each quadrant in various rows.

References Cited UNITED STATES PATENTS 3,070,842 1/1963 Fuller 264l09 ROBERT F. WHITE, Primary Examiner J. R. HALL, Assistant Examiner 

1.The method of felting wood wafers in waferboard production, which comprises directing the wafers on to a spinning cone within a confined space and be thrown radially off said cone into the open upper ends of a plurality of tubes arranged around the cone, the lower ends of said tubes arranged around the cone, the lower ends of said tubes being arranged in spaced rows extending transversely of and spaced above a path along which supporting plates are moved, said tubes distributing the wafers evenly on to the moving plates across the width thereof to form thereon felted mats of predetermined thickness and density. 